Safety latch for a cargo platform

Abstract

A safety latch for a cargo platform of the type particularly adapted to be mounted on the rear of a truck's cargo body. The cargo platform is pivotally mounted along its front edge to a combined elevating/storing mechanism which is of a chain and compounding sprocket type. In this type mechanism, the chain is taut as it holds the cargo platform in horizontal position when it functions as an elevator, and the chain is taut as it is compounded when it is desired to open and close the cargo platform between vertical storage and horizontal elevator positions. The safety latch cooperates with the cargo body, the chain, and the platform to insure that the platform is latched to the cargo body in its storage position when the chain is slack, i.e., not taut. The chain is always taut when the cargo platform is in the horizontal position and used as an elevator, as well as when the cargo platform is being swung between its elevator position and its vertical position. However, in the final vertical storage position the chain may go slack, and it is when that slackness occurs that the safety latch automatically interconnects with the platform and the cargo body to insure that the platform is retained in the vertical position.

Having described in detail the preferred embodiment of my invention, what I desire to claim and protect by Letters Patent is: 
     
       1. A cargo platform assembly comprising a mast assembly having a mast guide and a mast movably supported by said guide,   a motor for moving said mast relative to said mast guide,   a platform pivotally connected to said mast, said platform being swingable relative to said mast between an open position and a closed position,   a flexible tension member having one end connected to said platform and the other end connected to said mast, and a compounding wheel rotatably mounted at a stationary position relative to ground, said compounding wheel and said flexible tension member being relatively selectively positionable between a first position where the tension member is engaged by the compounding wheel for swinging the platform between open and closed positions as said mast moves relative to said mast guide and relative to ground, and a second position where the tension member cannot be engaged by the compounding wheel when the mast is moved relative to the mast guide for raising and lowering the platform as an elevator, and   a safety latch having one portion mounted on said mast and another portion mounted on said cargo platform, one of said two portions of said safety latch being biased against said flexible tension member so that it is latchingly connected with the other of said two portions when said platform is in its closed position and when said tension member is relaxed to prevent swinging movement of said platform toward its open position, and so that when said tension member is taut one of said two portions of said safety latch is disconnected from the other of said two portions of said safety latch to permit swinging movement of said platform toward its open position from its closed position.   
     
     
       2. A cargo platform assembly as set forth in claim 1, said latch comprising a sensor continuously biased against said flexible tension member, the tautness of said tension member as determined by said sensor causing said one of said two portions of said safety latch to be connected to or disconnected from the other of said two portions of said safety latch.   
     
     
       3. A cargo platform assembly as set forth in claim 2, said latch comprising a hook and a pin, said hook being mounted on one of said mast and said platform, and said pin being mounted on the other of said mast and said platform.   
     
     
       4. A cargo platform assembly as set forth in claim 3, the closed position of said platform being generally vertical relative to ground, and said mast being movable in a generally vertical path relative to ground. 
     
     
       5. A cargo platform assembly as set forth in claim 3, said latch being mounted on said mast, and said pin being mounted on said platform. 
     
     
       6. A cargo platform assembly as set forth in claim 5, said latch comprising an arm shaped element, one end of said arm mounting said sensor and the other end of said arm mounting said hook, said arm being pivotally connected at its elbow to said mast, and   a spring continuously biasing said arm against said flexible tension member.   
     
     
       7. A cargo platform assembly comprising a cargo platform,   a mechanism that operates said platform in elevator fashion when said platform is in a horizontal position, and that operates to move said platform into a storage position from said horizontal position, said mechanism being positionable in a relaxed attitude when said platform is stored that permits said platform to move uncontrollably from said storage position toward said horizontal position if said mechanism is operated while in said relaxed attitude and if no restraint is provided to said platform,   a safety latch connected to said assembly, said safety latch being automatically connected with said platform in response to movement of said platform into said storage position from said horizontal position so as to maintain said platform in said storage position if said mechanism is positioned in said relaxed attitude, and said safety latch being automatically disconnected from said platform to release said platform from said storage position when said mechanism is positioned in an activated attitude that permits said platform to move controllably from said storage position toward said horizontal position, and   a sensor connected with said safety latch, said sensor being adapted to sense when said mechanism is positioned in said activated attitude or in said relaxed attitude when said platform is in said storage position, said safety latch being disconnected from said platform in response to sensing of said mechanism in said activated attitude and being connected with said platform in response to sensing of said mechanism in said relaxed attitude.   
     
     
       8. A cargo platform assembly as set forth in claim 7, said latch comprising a hook and a pin, said hook being mounted on one of said mechanism and said platform, and said pin being mounted on the other of said mechanism and said platform.   
     
     
       9. A cargo platform assembly as set forth in claim 8, said latch having an arm shaped configuration, one end of said arm mounting said sensor and the other end of said arm mounting a hook, and a bias device continuously biasing said arm into sensing relation with said mechanism.   
     
     
       10. A cargo platform assembly comprising a mechanism for swinging a platform from a generally horizontal elevator position to a generally vertical position, for raising said platform in said vertical position to a full up intermediate storage position, and for lowering said platform in said vertical position slightly relative to said full up position into a final storage position,   a safety latch interconnected with said mechanism, said latch being movable between latch and unlatch positions, said latch automatically latching said platform in said final storage position in response to lowering of said platform from said full up storage position to said final storage position to prevent swinging of said platform toward a horizontal position while in said final storage position, and   a sensor connected to said safety latch, said sensor being adapted to sense when said mechanism is lowering said platform from said full up storage position into said final storage position and said sensor being adapted to sense when said mechanism is raising said platform from said final storage position to said full up storage position, said safety latch not being connected with said platform as said platform is lowered unless said sensor senses said platform being lowered to said final storage position.   
     
     
       11. A cargo platform assembly as set forth in claim 10, said assembly comprising a safety device selectively connectable with said platform and a support fixed at a location above ground, said connection so formed maintaining said platform above ground in said final storage position.   
     
     
       12. A cargo platform assembly as set forth in claim 11, said latch comprising a hook and a pin, said hook being mounted on one of said mechanism and said platform, and said pin being mounted on the other of said mechanism and said platform.   
     
     
       13. A cargo platform assembly as set forth in claim 12, said latch having an arm shaped configuration, one end of said arm mounting said sensor and the other end of said arm mounting a hook, and a bias device continuously biasing said arm into sensing relation with said mechanism.